The 62 mile (100 km) wide crater on the northwest wall of the Sea of Nectar is the youngest of the crater chain which also includes Cyrillus and Catharina. Its crater walls rise about 1300 yards (1200 m) above the surrounding area and even 5500 yards (5000 m) above the crater floor. The central mountain range extends at least 2200 yards (2000 m) above the crater floor and measures 19 miles (30 km) in diameter.

In the south, Theophilus superimposes the older crater Cyrillus. The 3800 yard (3500 m) high crater walls of Cyrillus are also damaged by another, 11 mile (17 km) wide crater. In the center of the 58 mile (93 km) wide Cyrillus, the central peak is still preserved.

South of Cyril, Catharina as the oldest crater of the trio concludes this striking small crater chain. The 60 mile (97 km) wide crater has a quite smooth 3300 yard (3000 m) high wall. Especially the western part of the crater is covered by smaller craters and hills.